1. Field of the Invention
This invention generally relates to a rolling contact bearing assembly including a rail and a slider which travels along a predetermined path as guided by the rail, and, in particular, to a linear motion rolling contact bearing assembly which allows a slider to move along a predetermined path defined by a rail in rolling contact therewith no matter how long the path is.
2. Description of the Prior Art
A linear motion rolling contact bearing assembly is well known in the art as disclosed in the Japanese Utility Model Laid-open Pub. No. 59-172825. A linear motion rolling contact bearing assembly includes a rail which extends straight over a predetermined length to define a predetermined path along which a slider travels. Typically, the rail is U-shaped in transverse cross section and the slider is located in the space defined by the U-shaped rail. That is, a pair of guide grooves is provided in the opposite side walls of the U-shaped rail to define the predetermined path. And, the slider is provided with a pair of endless circulation paths in which a number of rolling members are provided. Each of the endless circulation paths includes a straight load path section opposite to the corresponding one of the pair of guide grooves, a return path section in parallel with the load path section and a pair of curved connecting path sections, each connecting the corresponding ends of the load and return path sections. Thus, when the rolling members are located in the load path section, they are brought into rolling contact with the guide grooves formed in the guide rail so that the slider may travel in either direction while keeping rolling contact with the guide grooves of the rail. Typically, the rolling members are either spherical balls or cylindrical rollers, though modifications of these or any other types of rolling members may also be used.
In such a linear motion rolling contact bearing assembly, a plurality of rolling members must be provided in the pair of endless circulation paths of the slider and thus the slider must be defined in a split format. And, thus, since the slider is manufactured by assembling parts, for example, using bolts, rivets or the like, the slider cannot be manufactured with close tolerances. Accordingly, the guide grooves of a rail cannot be made at high accuracy, either, in order to accommodate the tolerance of the slider. As a result, a prior art linear motion rolling contact bearing assembly tended to be low in accuracy and thus was limited in the field of applications. For example, the prior art linear motion rolling contact bearing assembly was not suited for applications, such as high precision measuring equipment, small-scale high precision machine tools and electronics equipment.